During the last week Chandra's observing schedule was interrupted by a
spacecraft safemode event that occurred at 11:33pm EDT on May 28. The
safemode transition was identified at the first contact after the
event, which started at 8:00am EDT on May 29. The safemode transition
was nominal and all systems functioned as expected.

The cause of the safemode was a trip of the sun-position
monitor. Telemetry showed that the fine-sun-sensor (FSS) began to
produce erratic data as the spacecraft pitch-angle neared the edge of
the FSS field-of-view (FOV). Analysis of the FSS data and the monitor
logic indicates that both a region check and a comparison check with
the coarse-sun-sensor data failed, which led to the trip. The observed
behavior is consistent with expected FSS operation near the boundary
of the FOV. There were no hardware failures. The possibility of a
slight variation in the FSS FOV, which is being investigated and
mission planning processes have been updated to increase the margin
from the edge of the FOV. Since the safemode was not initiated by a
hardware fault, the Chandra Operations team completed the safemode
recovery procedure to the prime hardware at 9:30am EDT on May 30. The
team completed the clean-up activities, transition to attitude control
by pointing at stars, a fine attitude update required to resume
science operations following the safemode, and a maneuver to an
attitude to prepare for observing at 11:20pm on May 30. A new mission
schedule and loads were approved and began operating at 3:50pm on May
31 with 193.0ks of science loss. The new loads included an observation
of NGC 4088 ULX 1, which was accepted as a Director's Discretionary
Time TOO on May 25. Scheduled observations of PLCKG266.6-27.3, ALPHA
CEN, G21.5-09, Ruprecht 147, GJ 191, and G313.87-17.10 were impacted
by the safemode and will be rescheduled.

A flight software patch was uplinked on May 30 to modify the RadMon
process to use a flag generated by ACIS as a new channel used to
monitor for high radiation. The step was taken to counter degradation
in the EPHIN radiation detector due to increasing temperature trends
through the mission. Real-time procedures were executed on may 31 to
dump OBC-A memory as a follow-up to this patch and patching done
during the safemode recovery. The dump will be used to update the
baseline memory image maintained on the ground.

The schedule of targets for the next week is shown below and includes
an observation of 4U 1630-47, which was accepted as a Director's
Discretionary Time TOO on May 24, an observation of MAXI J0556-332,
which was accepted as a Target of Opportunity on May 8, an observation
of RXJ1622.7-2325_P1 coordinated with OVRO/CARMA, and an observation
of M31* coordinated with HST and the EVLA.